One of the most critical problems associated with intensive agricultural activities has been the degradation of the natural environment due to the overuse of chemical fertilizers. Research has shown that the potential problems associated with the overuse of chemical fertilizers may outweigh the benefits of increases in crop production. However, despite this, it has been predicted that “the use of chemical fertilizers must be expanded two- to threefold to maintain soil fertility and productivity in the developing countries over the next 25 years if the world is to feed itself.” Dr Norman Borlaug Nobel Peace Prize recipient.
There are a number of reasons why increased use of chemical fertilizers has been predicted, including increased human population and the replacement of traditional foods with cereals like wheat. However, a more worrying reason is that yields from traditional agricultural lands are falling. Although the reason for this is not known, even more chemical fertilizer has usually been used in an attempt to reverse the trend. However, one factor that has been noted is that the amount of topsoil in these areas has steadily been declining, and that normal microbial activity is reduced.
One area of agriculture that traditionally utilizes large quantities of chemical fertilizers is monoculture crop production. Monoculture crops include sugarcane, cereals such as wheat and barley, and turf. Turf production especially uses large amounts of chemical fertilizers. Turf production, as typified in golf courses, race courses, public areas and parkland management, involves the maintenance of the appropriate nutrient levels in the soil, management of the sub-soil structure, protection against invasive fungal diseases, and development of a turf bed that is appropriate for the application (Crockford, 1992). The protocols used often place heavy emphasis on the use of inorganic nutrients, the use of fungicides, and intense mechanical interventionist procedures to produce satisfactory long-term results.
Another problem associated with turf production is the continual loss of N, P, K and other nutrients from grass clippings. The extensive use of sandy substrata limits the retention of added inorganic nutrients, as sand provides few binding sites for the adhesion of inorganics. The addition of fungicides and chemicals to control fungal infestations is common practice, and the lack of organic complexity-leads to low cation exchange capacity (CEC), making it more likely that these inorganic nutrients can leak into the water table. In addition, the permeability of the subsoil means that water utilisation is inefficient and energy usage through irrigation systems is relatively high.
The production of turf and other monoculture crops has, like many others, seen a decline in yield in recent years (Magarey, 1994). Usually this decline has been regarded as a result of disease rather than attributed to the use of chemical fertilizers, and has been dealt with in four ways:    1) Chemically, by the use of fumigation and fungicides;    2) By the use of disease-resistant plants;    3) By rotation or fallowing; and    4) Biological control (Weller, 1988).
While these approaches have not solved the problems of decline in yield, they have produced some interesting observations. Many studies have suggested that root health and, to a lesser extent, soil organic matter levels, are the main contributing factors to the growth of various plants (Papavizas and Lumsden, 1980). Moreover, it has been seen that declining monoculture yield seems to occur when continuous cropping with a susceptible crop results in disease.
However, it has also been observed that in some instances the disease-causing pathogen may create a favourable environment for multiplication of other microorganisms that are its natural enemies. This can occur because an adequate food base for the progressive development of microorganisms antagonistic to the pathogen is produced.
In some soil, disease does not occur in susceptible host plants even though the pathogen is present, or is introduced into the soil. Such soils are referred to as suppressive and have been reported for several fungal pathogens such as Phytophthora spp, Fusarium spp, Gaeumanomyces spp, and Rhizoctonia spp for example. In soils that are generally suppressive, the suppressive character is probably due to the entire microflora acting as a brake on the growth and propagation of the pathogen(s). Specific suppressiveness occurs when one or two organisms control the pathogen through specific mechanisms (Cook, 1993).
In the case of turf, it has been shown that the severing of the leaf tips during mowing may provide an entry point for fungi such as Rhizoctonia and Fusarium spp which then colonise and debilitate the plants (Spurr and Knudsen, 1985; Schisler and Slininger, 1994; Kahl, 1978). However, suppressive compost mixtures have been developed which can combat some of these effects.
It has been suggested that suppressiveness may also be due to the architecture of plant resistance mechanisms due to the accumulation of some particular chemical elicitor(s). This has been suggested as an important means of disease control in plants (Cartwright et al., 1977; Schönbeck and Dehre, 1986). Barley can activate a number of resistance mechanisms in response to attempted penetration by powdery mildew. These include the development of papillae with fluorescent haloes (Thordal-Christensen et al., 1988), accumulation of inorganic compounds (Kunoh and Ishizaki, 1976), increased peroxidase activity (Kerby and Somerville, 1989), formation of phenolics (Shiraishi et al., 1989) and the synthesis of proteins that appear to be a response to the pathogen (Apel et al., 1990; Bryngelsson and Green, 1989).
Glucans have also been shown to elicit an immune response in animals, crustaceans and plants. This may be due to the fact that glucans are present in the cell wall of many fungi, and attachment of exogenous glucan to plant receptor sites may mimic the attachment of pathogenic fungi. Growth factors may also stimulate plant protection mechanisms; see for example our earlier application WO97/02356 the entire disclosure of which is incorporated herein via reference. During vigorous growth, cell multiplication and extension of tissue provides greater access to invasive pathogens. This enhances the systems designed to cope with stress.
All of these observation have led researchers to conclude that enhancing the well-being of the rhizosphere may be as important as providing nutritional support for the plants through fertilization. In other words, crop yields may be reduced in those areas that utilize the most chemical fertilizers, because chemical fertilizers do not provide adequate resources for the natural microflora and fauna to proliferate. Without such microorganisms there is a greater incidence of root disease and pathogenic infection.
Accordingly, there, is a need for an alternative to chemical fertilizers which increases crop production, while minimizing the degradation of the environment. In particular, there is a need to have an alternative that reduces the incidence of disease in plants, improves root health and improves the levels of organic matter in the soil.
One alternative that has been actively pursued in recent times is organic fertilizers. Generally, organic fertilizers are more environmentally friendly, while still providing very good nutritional support for plants. Furthermore, it has been shown that organic fertilizers have an added benefit in that they are capable of promoting the growth of soil microbes. These microbes often produce antibiotics that are capable of deterring the growth of non-beneficial soil fungi, thereby preventing diseases of vegetables and lawn grass.
Some microorganisms, like Trichoderma and Mycorrhiza, aid a plant's uptake of water and nutrients and stimulate its growth, while others assist in:
1. Decomposition of crop residues, manure and other organic material;
2. Retention of nutrients;
3. Nutrient recycling;
4. Biological control of root rot and parasitic nematodes;
5. Production of plant growth regulators; and
6. Soil structure and tilth.
A further benefit of using organic fertilizers is that they are generally made from industrial wastes or animal effluent. These wastes have, for many years, been a source of environmental pollution in their own right; however, as increased negative data have been obtained about the use of chemical fertilizers, the use of organic wastes to make organic fertilizers has increased. Unfortunately, not all organic wastes are useful as organic fertilizers, and the processes involved in turning these into fertilizers can be costly. Accordingly, while the use of organic fertilizers is increasing, and the need for such organic fertilizers is evident, an appropriate source of “cheap” raw material has not been found to date.
One source of cheap raw material is waste by-products from the brewing and fermentation processes. Some attempts at utilizing these wastes have been undertaken in the past. For example, one by-product that has been used in the past is the spent grain left over from the beer brewing process. Spent grain is a mixture recovered after separation of the wort extract by filtration through a mash filter, a Lauter Tun or similar device.
Another by-product from the beer brewing industry that has been used is the liquid waste after fermentation has been undertaken. This waste usually requires treatment steps with high energy or chemical input, and often the waste at this stage has had many of the nutrients removed. For example, Japanese Patent No. JP75002901 by Takara Shugo Co. Ltd. describes the use of waste liquid from brewing. The waste liquid was described as containing yeasts, non-fermentable sugars, proteins, organic acids, and potassium. However, the waste liquid used was obtained via a condensation process after fermentation of molasses, and the recovered material was calcined at 850° C. This process is not only energy-intensive, but all of the protein, enzymes, plant hormones and naturally present microorganisms are destroyed by the fermentation and calcination processes, resulting in a fertilizer which is potentially no better than a “normal” chemical fertilizer. Indeed, such a preparation would have low levels of sugars, dextrins, proteins, and vitamins.
Accordingly, the present invention attempts to overcome or at least alleviate some of the problems associated with providing a cheap, organic fertilizer which not only provides adequate nutritional support for plants, but also encourages the proliferation of soil microorganisms, thereby improving soil condition.
The applicant has now surprisingly found that malt extract, termed “brewer's extract” and/or spent grain liquor, are capable of stimulating plant growth and appearance, while dramatically improving soil structure and function. Moreover, it has also been found that spent grain liquor acts antagonistically against some examples of known pathogenic fungi. While some of these results may be attributable to the nutrient levels in these preparations, the results in the main are not solely ascribed to these nutrients as the visual appearance of plants are dramatically improved compared to the appearance of plants treated with traditional inorganic fertilisers plus biocide regimes.